As is well known, the typical thermometer in present use is made from a glass tube in which mercury or another suitable expansible fluid for indicating temperature is contained in a reservoir and is free to expand into a capillary passage through a constriction which is adapted to maintain the expansible fluid in the capillary passage upon subsequent cooling of the thermometer unless the fluid is "shaken down". When glass thermometers are used, there is, of course, the ever present danger of breakage either during handling or use of the thermometer. Particularly for clinical use, this risk of breakage is especially dangerous with glass mercury thermometers because of the possibility of ingestion or introduction of glass fragments and because of the toxicity of mercury. Moreover, the repeated use of glass thermometers by the same individual or different individuals requires repeated sterilization and increases the possibility of cross-contamination due to of inadequate or incomplete sterilization of the thermometer. This problem is particularly acute in hospitals, clinics and the like. Therefore, several attempts have been made in order to provide a disposable thermometer, thus eliminating the sterilization problem. However, production of a conventional glass-mercury thermometer is rather complicated and therefore expensive because of the construction of the thermometer, especially the constriction, and because of the components involved, especially the mercury. Therefore, a conventional glass-mercury thermometer may not be used as a disposable, maximum reading thermometer, firstly for economical reasons, and secondly, for environmental and pollution reasons.
Because of the above-described inherent problems associated with glass-mercury thermometers, various types of non-breakable, non-mercury thermometers have been proposed some of which have been constructed basically identically to conventional glass-mercury thermometers, thus including the above-described constriction. However, non-breakable, non-mercury, disposable maximum reading thermometers constructed basically identically to conventional breakable, mercury-glass thermometers have not been commercially accepted, primarily for economic reasons.
Several attempts to provide a disposable, maximum reading thermometer of the non-breakable, non-mercury type have been carried out in order to provide a more simple construction than the one known from conventional glass-mercury thermometers, thus eliminating the above-described constriction. However, these attempts have not hitherto provided commercially accepted disposable maximum reading thermometers guaranteeing a reliable and lasting indication of the maximum temperature.
Therefore, it is an object of the present invention to provide a disposable maximum reading thermometer of the above-described kind which is capable of providing a lasting and highly accurate maximum temperature indication and which may be produced in an economic way.